Measurement of spin correlation in ttbar production using a matrix element approach

TL;DR

This paper presents the first measurement of top-antitop quark spin correlation using a matrix-element-based approach in proton-antiproton collisions, confirming the Standard Model prediction.

Contribution

It introduces a novel matrix-element method to study ttbar spin correlation, providing a new technique in top quark physics analysis.

Findings

Results agree with Standard Model predictions.

Uncorrelated spin hypothesis excluded at 97.7% confidence level.

First application of matrix-element approach to ttbar spin correlation.

Abstract

correlation, assuming that the spin of the top quark is either correlated with the spin of the anti-top quark as predicted by the standard model or is uncorrelated. For the first time we use a matrix-element-based approach to study ttbar spin correlation. We use {ttbar -> W+bW-bbar ->l+nubl-nub} final states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96 TeV, where l denotes an electron or a muon. The data correspond to an integrated luminosity of 5.4 fb-1 and were collected with the dzero detector at the Fermilab Tevatron collider. The result agrees with the standard model prediction. We exclude the hypothesis that the spins of the ttbar are uncorrelated at the 97.7% C.L.